1. Technical Field
The present invention relates generally to hydrodesulfurization, hydrodenitrogenation, and/or saturation of double bonds in liquid streams. More particularly, the present invention relates to a high shear system and process for improving hydrodesulfurization, hydrodenitrogenation, and/or saturation of double bonds of liquid streams.
2. Background of the Invention
Hydrotreating refers to a variety of catalytic hydrogenation processes. Among the known hydroprocesses are hydrodesulfurization, hydrodenitrogenation and hydrodemetallation wherein feedstocks such as residuum-containing oils are contacted with catalysts under conditions of elevated temperature and pressure and in the presence of hydrogen so that the sulfur components are converted to hydrogen sulfide, the nitrogen components to ammonia, and the metals are deposited (usually as sulfides) on the catalyst.
Recent regulatory requirements regarding levels of sulfur in fuels, diesel and gasoline, have created a greater need for more efficient means of sulfur removal. The feedstocks that are subjected to hydrotreating range from naphtha to vacuum resid, and the products in most applications are used as environmentally acceptable clean fuels.
Characteristic for hydrotreatment operations is that there is essentially no change in molecular size distribution, in contrast to, for instance, hydrocracking. Hydrodesulfurization (HDS) is a sub category of hydrotreating where a catalytic chemical process is used to remove sulfur from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur is to reduce the sulfur oxide emissions that result from the use of the fuels in powering transportation vehicles or burning as fuel. In the petroleum refining industry, the HDS unit is also often referred to as a hydrotreater. In conventional hydrodesulfurization, carbonaceous fluids and hydrogen are treated at high temperature and pressure in the presence of catalysts. Sulfur is reduced to H2S gas which may then be oxidized to elemental sulfur via, for example, the Claus process.
While hydrodesulfurization (HDS) is assuming an increasingly important role in view of the tightening sulfur specifications, hydrodenitrogenation (HDN) is another process that hydrocarbon streams may also undergo in order to allow for efficient subsequent upgrading processes. Hydrofinishing or polishing hydrocarbon streams by, for example, saturating double bonds is also an important upgrading process, especially for naphthenic streams.
In addition to its removal for pollution prevention, sulfur is also removed in situations where a downstream processing catalyst can be poisoned by the presence of sulfur. For example, sulfur may be removed from naphtha streams when noble metal catalysts (e.g., platinum and/or rhenium) are used in catalytic reforming units that are used to enhance the octane rating of the naphtha streams.
Many of the previous methods and systems for removing sulfur-containing compounds from carbonaceous fluids may be costly, include harsh reaction conditions, may be inadequate for the removal of substantial amounts of sulfur-containing compounds, may be ineffective for the removal of sulfur-containing compounds having certain chemical structures, and/or may not be easily scaled-up to large fluid volumes.
Accordingly, there is a need in the industry for improved processes for hydrodesulfurizing, hydrodenitrogenating, and hydrofinishing carbonaceous fluid streams.